The present invention is concerned with rotating annular turbomachinery components. Specifically, the present invention is concerned with compressor discs of a gas turbine or an aero engine fan. By turbomachinery we mean machines that transfer energy between a rotor and a fluid, including turbines, fans and compressors.
When an annular component is rotated, various stresses are developed in the component as a result of the rotational motion. For example radial stresses are generated in the radial direction of the component as it rotates.
Hoop stresses are also generated in rotating annular components. The magnitude of hoop stress observed at a given radius in a rotating annular component is dependent on both the inner and outer radius of that component. Specifically, as either the inner or outer radius of the component is made larger, the hoop stresses generated at given radius will increase.
For an annular component with a given inner and outer radius however, the maximum hoop stress is observed at the inner radius, and reduces towards the outer radius.
As such, an annular component with a small inner radius has a lower maximum hoop stress than an annular component with a larger inner radius (providing the outer radius is the same).